Where did the server go?

With version 0.6 onwards the API Star project is being focused as a
framework-agnositic suite of API tooling. The plan is to build out this
functionality in a way that makes it appropriate for use either as a stand-alone
tool, or together with a large range of frameworks.

The 0.5 branch remains available on GitHub, and can be installed from PyPI
with pip install apistar==0.5.41. Any further development of the API Star
server would likely need to be against a fork of that, under a new maintainer.

If you're looking for a high-performance Python-based async framework, then
I would instead recommend Starlette.